Image 27


original	lighter	colour coded

and with an inserted data grid:

(in the middle of tiles, median of raw G-pixels values is given, the bottom value is the tile luminance divided by one candela per square meter).

# Date/Time    : 2006:06:29 02:47:38
# Resolution   : 1280 x 960 in jpeg (1424x1076 in pgm/27.pgm)
# Focal length : 13.6mm  (35mm equivalent: 92mm)
# CCD width    : 5.32mm
# Exposure time: 2.000 s 
# Aperture     : f/3.2
# ISO equiv.   : 200

# Selected image percentils         L=(1.730*0.35*R+1.000*0.65*G+1.570*0.00*B)* 2.17E-4
# %    R     G1    G2    B readings  R        G        B        L / cd/m2
  1   -37   -34   -33   -46        -0.0139  -0.00727  -0.0157  -0.00958
 10     0     0     0   -10         0.00     0.00    -0.00341   0.00  
 50   216   175   174    50         0.0811   0.0379   0.0170   0.0530
 90  2709  1999  1998   291         1.02     0.434    0.0991   0.638 
 99  3388  2511  2513   402         1.27     0.545    0.137    0.799 
100 15869 15866 15866 15867         5.96     3.44     5.40     4.32  
# flux from 0.115*0.92 sr ( 1.51E-7 sr/4px) is  0.0235 lx ( 0.0240 lx tilewise);
# tilewise luminance  0.234 cd/m2 with rel. SD  114 % (summing pixels below 15850 and with non-zero green: there is 91.7 % of them)
# Fuji Devignetting: 2 # dark frame dark/43.pgm subtracted from all values
# Red  average= 926.3  minimum= -108  maximum=15869   over 15850: 406 zero:  6.3 %
# GrUp average= 706.9  minimum=  -96  maximum=15866   over 15850: 349 zero:  8.5 %
# GrDw average= 704.2  minimum= -110  maximum=15866   over 15850: 322 zero:  8.1 %
# Blue average= 117.2  minimum= -126  maximum=15867   over 15850:  51 zero: 14.0 %

End of results of "raw2lum" (version 1.22) with parameters:
  -c fuji -fa -d dark/43.pgm -sm100 -nh -nt -i 27.txt -e 27.eps -n 27.ppm -t 118 -s71:76 pgm/27.pgm

Logarithmic luminance scale (the unit is candela per square meter) – intensities of snow illuminance in lux would be obtained by multiplying the numeric value of luminance by 3.6. For asphalt, such a coefficient is between 20 and 40 (or much less, for specular reflection of distant lamps)